1. Field of the Invention
The present invention relates to an optical disc player, and more particularly to an optical disc recording/playing apparatus and method for improving data recording capacity and compatibility of an optical disc.
2. Description of the Prior Art
An optical disc recording/playing apparatus generally records data on an optical disc and retrieves the recorded data by scanning portions of the optical disc by a laser beam converged via an optical pick-up, wherein the optical pick-up focusing, tracking and the spinning rate of the optical disc are controlled.
In a play-only optical disc such as a compact disc (CD), an information signal is continuously recorded in the form of pits formed along a spiral track of the disc. That is, the general optical disc recording/playing apparatus scans a focused laser beam to a signal pit of an optical disc and carries out tracking control for detecting a synchronous signal of a channel bit signal array, and compares the frequency and phase of the detected synchronous signal with those of a standard synchronous signal to thereby detect a control signal for controlling the spinning rate of the optical disc.
As shown in FIG. 1, a conventional optical disc playing apparatus includes: a turntable 2 which accommodates an optical disc 1 placed thereon; an optical pick-up 3 for projecting a laser beam to the optical disc 1, detecting the laser beam reflected against the optical disc 1, and converting the detected value into electrical signals a, b, c, d, e and f; a laser stabilizer 4 for stably transmitting a laser beam to the optical pick-up 3; a playback signal processor 5 for receiving the electrical signals a, b, c, d, e and f output from the optical pick-up 3 and generating a focus control signal Fe, a tracking control signal Te and a radio frequency generating signal RF; a focusing controller 6 for performing a focus control of the optical pick-up 3 in accordance with the focus control signal Fe output from the playback signal processor 5; a tracking controller 7 for performing tracking control in accordance with the tracking control signal Te output from the playback signal processor 5; a channel bit signal processor 8 for zero-crossing the radio frequency generating signal RF output from the playback signal processor 5 to-thereby produce a square wave signal and detecting a channel bit row signal CHBr and a synchronized signal of a channel bit row SYNr; a digital signal processor 9 for decoding the detected channel bit row signal CHBr and performing error correction so as to convert such signal into digital data; a standard clock signal generator 10 for generating a standard synchronized signal SYNs; a motor control signal generator 11 for generating a motor control signal Me by comparing the standard synchronized signal SYNs output from the standard clock signal generator 10 with the channel bit synchronized signal SYNr output from the channel bit signal processor 8; and a motor controller 12 for controlling a motor 13 in accordance with the motor control signal Me output from the motor control signal generator 11.
The optical pick-up 3 includes: a laser diode LD for generating a laser beam; a grating GR for branching the laser beam output from the laser diode LD into a main beam and a pair of subbeams for controlling a tracking servo; a beam splitter BS for splitting the beam from the laser diode LD and the beam reflected against the disc; an object lens OL for converging the three laser beams passing through the beam splitter BS onto a portion of a signal track of the disc; a focus activator FA and a tracking activator TA for moving the object lens OL in the direction of tracking and/or focusing so that the object lens OL can accurately converge the three laser beams onto a signal track of the disc; a wolla stone prism WP for reflecting a beam which has been reflected from the disc and has passed through the beam splitter BS; a sensor lens SL for converging a beam reflected from the wolla stone prism WP; and a photo detector PD for converting the laser beam converged by the sensor lens SL into electrical signals a,b,c,d,e and f.
With reference to the accompanying drawings, the operation of the thusly composed conventional optical disc playing apparatus will now be described.
First, when the laser diode LD of the optical pick-up 3 generates a laser beam under the control of the laser stabilizer 4, the grating GR branches the laser beam into a main beam and a pair of subbeams for the tracking servo. Then, the beam splitter BS projects the three beams toward the object lens OL.
The object lens OL converges the three beams projected thereto through the beam splitter BS onto a signal track of the disc, and a beam reflected from the portion of the signal track of the disc is converged passing sequentially through the beam splitter BS and the wolla stone prism WP to the sensor lens SL. The beam passing through the sensor lens SL is converted by the photo detector PD into electrical signals a,b,c,d,e and f.
At this time, the focus activator FA and the tracking activator TA move the object lens OL in the direction of tracking and/or focusing in order for the object lens OL to accurately converge the three beams.
That is, as shown in FIG. 2A, when the object lens OL projects the three beams onto a signal track of the disc, the main laser beam LB is positioned directly on a pit row of the signal track as shown in FIG. 2B, and the other two subbeams LBr, LBl are respectively positioned on the left and right sides of the main beam LB. At this time, assuming that a track pitch Tp denotes an intertrack distance, the pair of subbeams LBr, LBl are positioned to be 0.25 Tp away from the track, respectively.
As shown in FIG. 2C, the photo detector PD includes a main photo detecting element for detecting the amount of the reflected main laser beam LB and secondary photo detecting elements for detecting the reflected subbeams. At this time, the main photo detecting element is partitioned to form four photo detecting elements PDA-PDD, and the pair of secondary photo detecting elements PDE, PDF are respectively provided above and below the main photo detecting elements PDA-PDD.
The main photo detecting elements PDA-PDD of the photo detector PD detect the amount of reflected main laser beam LB to generate electrical signals a,b,c,d and the secondary photo detecting elements PDE, PDF detect the amount of the reflected subbeams LBr, LBl to generate electrical signals e,f.
The playback signal processor 5 receives the electrical signals a to f detected in the photo detector PD and obtains a radio frequency generating signal RF by summing the signals a through d (a+b+c+d). A focus control signal Fe is obtained using the equation (a+c)-(b+d), and by subtracting f from e (e-f), a tracking control signal Te is obtained.
The focus controller 6 operates the focus activator FA of the optical pick-up 3 in accordance with the focus control signal Fe output from the playback signal processor 5, and the tracking controller 7 operates the tracking activator TA of the optical pick-up 3 in accordance with the tracking control signal Te of the playback signal processor 5.
The channel bit signal processor 8 zero-crosses the radio frequency generating signal RF output from the playback signal processor 5 and converts the same into a round wave signal, to thereby detect the channel bit row signal CHBr and the channel bit synchronized signal SYNr. At this time, the channel bit row signal CHBr is decoded, error-corrected, converted into digital data in the digital signal processor 8 and processed according to various applications.
The motor control signal generator 11 generates a motor control signal Me by comparing the standard synchronized signal SYNs output from the standard clock signal generator 10 with the channel bit synchronized signal SYNr output from the channel bit signal processor 8, and in accordance with the motor control signal Me the motor controller 12 controls the motor 13 to thereby control the spinning speed of the optical disc 1.
In blank optical discs used for recording signals thereon, information signals such as channel bit signals are not recorded as in compact discs, but auxiliary signals are recorded thereon which is free-formatted according to a certain standard so as to control the tracking and the spinning speed of the optical disc. At this time, the free formatted auxiliary signals include a record signal, an address information signal for denoting the location of a corresponding track and a pilot signal for controlling the spinning speed of the disc. In this case, a track having lands and grooves is formed to control tracking, and tracking control signals are obtained therefrom.
The pilot signal having a certain cycle is recorded along the lands and grooves of the track, and the spinning speed of the disc is determined by detecting the cycle of a read pilot signal. In accordance with the determined spinning speed, data is recorded at a certain speed and density. In this case, random recording is possible because address information signals defining a serial location on the track are recorded.
In an orange book of the compact disc there is a standard for recording and playing spare signals free-formatted by a wobbling method in which, as shown in FIG. 3, a periodic wobbling in a free-formatted standard is applied to the lands or grooves of the track for denoting a pilot signal to detect the spinning speed of the disc and records an address information signal by phase-modulating the wobbling signal.
Then, data is recorded in the signal tracks having wobbled grooves and the main laser beam LB for reading the information is positioned on the signal track. The pair of subbeams LBr, LBl for detecting a tracking control signal are positioned on the left and right side from the main beam LB to thereby detect the beam reflected against the signal track.
Meanwhile, the technological developments of the optical disc and its player have been made to improve data storage capacity by resolving intertrack interference.
There are no problems when recording a wobbling signal on lands of a track by using a wobbling method, however, when recording information in the grooves of a track, problems due to undesired reading of different wobbling signals recorded on the lands next to a groove occur and a pilot signal for controlling the motor is not properly detected. Conversely, when recording a wobbling signal in a groove of the track, there also occurs a problem in recording information on a land of the track.
Therefore, a constant angle velocity CAV control method or a zoned CAV control method are recommended, but due to a low recording capacity these methods are known to be inappropriate for recording/playing a large amount of data which must be serially reproduced as in the case of video image data or voice data.
Further, when recording and using a free-formatted pilot signal on the disc, only a recording/playback apparatus having the proper pilot signal standard can be employed as an optical disc player and a recording capacity of a disc is restrictively confined by set standards.